This application claims priority from Japanese Application 2001-10622 filed Jan. 18, 2001 and Japanese Application 2001-76314, filed Mar. 16, 2001, the entireties of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device and a method of producing the same.
2. Description of the Background Art
As one form of piezoelectric/electrostrictive device, there is known a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts and a fixing part that connects the movable parts with each other at one end thereof and a piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base. There is also known a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, and a mounting part that connects the movable parts with each other at the other end thereof and a piezoelectric/electrostrictive element disposed on at least one side of the movable parts of the base. The above-mentioned piezoelectric/electrostrictive devices are disclosed in the specification of European Patent EP1017116A2.
The piezoelectric/electrostrictive device of such a form has a function of operating the movable parts caused by the displacement operation of the piezoelectric/electrostrictive element or a sensing function of sensing the displacement of the movable parts input from the side that is sensed, with the use of the piezoelectric/electrostrictive element. By effectively using these functions, the piezoelectric/electrostrictive device is used in a wide range of fields, such as thosedescribed below.
Piezoelectric/electrostrictive devices of such a form are used as active elements such as various transducers, various actuators, frequency region functional components (filters), transformers, vibrators and resonators for communication or mechanical power, oscillators, and discriminators, various sensor elements such as supersonic wave sensors, acceleration sensors, angular velocity sensors, impact sensors, and mass sensors, and various actuators that are put to use for displacement, positioning adjustment, and angle adjustment mechanism for various precision components of optical instruments and precision apparatus.
Piezoelectric/electrostrictive devices are formed typically by cutting a device master into a suitable size, and the device master is constructed by bonding a piezoelectric/electrostrictive element onto both of the front and rear surfaces of a base master via an adhesive, or is constructed by integrally forming these. Here, the base master is constructed by laminating and baking plural sheets.
Thus, the piezoelectric/electrostrictive device having such a form has a large number of construction components, so that the device is produced at a high cost and through a cumbersome assembling work. Moreover, since the construction components are bonded via an adhesive, there arises a variation of adhesion between the construction components, giving rise to a fear that the device characteristics may be adversely affected.
Further, the piezoelectric/electrostrictive device having such a form is produced by adopting means to cut a device master suitably into a large number of devices. Therefore, the piezoelectric/electrostrictive devices formed by cutting are contaminated with dusts generated at the time of cutting, cutting liquid, and organic components such as an adhesive or wax used for holding the device master at the time of cutting, so that it is not easy to clean the piezoelectric/electrostrictive device.
Also, in the case where the base is constructed with ceramics, one must adopt a hard ceramic material such as zirconia, since the ceramics are liable to be split. Even if a hard ceramic material is adopted, one must choose a suitable cutting condition to prevent a loss of material through nicks or cracks. Further, since the base is made of a hard ceramic material, the machining process is difficult to be designed and, in order to increase the number of machining products, one must give a careful consideration such as use of a large number of machining apparatus having different functions.
The base can be constructed with a metal material. The use of a metal material, however, gives rise to an oxidized end surface caused by friction heat during the cutting process and burrs remain on the processed end surface. Consequently, another processing step must be added to remove the burrs. Further, the piezoelectric/electrostrictive element can be tested only after the device master is cut.
Meanwhile, the device cut out from the device master is preferably cleaned by adopting ultrasonic cleaning that can easily remove the contamination. However, if a strong ultrasonic wave is used to obtain a high cleaning effect in ultrasonic cleaning, the device may be damaged, and the piezoelectric/electrostrictive element may be broken or peeled off from the base. For this reason, if the ultrasonic cleaning is adopted, one must select a weak ultrasonic wave that does not give damages to the device. However, if such a cleaning condition is adopted, a long period of time is needed in removing the contamination that has adhered at the time of cutting.
Dust generation from the piezoelectric/electrostrictive device may cause the following problems. For example, in the case where the piezoelectric/electrostrictive device is used in an actuator of a magnetic head in a hard disk drive, if dust is generated in the drive, the dust may cause crash of the floating slider onto the medium, thereby raising a fear of data destruction. Also, for the piezoelectric/electrostrictive device itself, the dust may adhere to the electrode of the piezoelectric/electrostrictive element, thereby giving rise to a fear of short circuit. For this reason, a high level of cleaning is required not only in the hard disk drive but also in the device itself.
Therefore, an object of the present invention is to solve the aforementioned problems of the prior art by allowing the base constituting the piezoelectric/electrostrictive device of that form to have an integral structure using one sheet of flat plate as an original plate.
The present invention relates to a piezoelectric/electrostrictive device and a method of producing the piezoelectric/electrostrictive device. The piezoelectric/electrostrictive devices according to the present invention are piezoelectric/electrostrictive devices provided in the following three forms.
A piezoelectric/electrostrictive device of the first form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts and a fixing part that connects the movable parts with each other at one end thereof. A piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.
A piezoelectric/electrostrictive device of the second form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, and a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof. A piezoelectric/electrostrictive element disposed on at least one side of the movable parts of the base.
A piezoelectric/electrostrictive device of the third form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof, and a connecting part that is integral with the mounting part and surrounds the mounting part, the movable parts, and the fixing part. A piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.
In the piezoelectric/electrostrictive device of the first form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part has a flat plate shape; and the movable parts are erect by a predetermined height from side peripheries of the fixing part to face each other and extend beyond the other end of the fixing part along the side peripheries of the fixing part.
The piezoelectric/electrostrictive device can be constructed in such a manner that a slit-shaped groove extending from the other end of the fixing part intervenes between a base part of the movable parts constituting the base and the side peripheries of the fixing part. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape.
In the piezoelectric/electrostrictive device of the second form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part and the mounting part have a flat plate shape; and the movable parts are erect by a predetermined height from side peripheries of the fixing part and the mounting part to face each other and extend along the side peripheries of the fixing part and the mounting part.
The piezoelectric/electrostrictive device can be constructed in such a manner that a laterally extending slit-shaped groove intervenes between the other end of the fixing part and the one end of the mounting part constituting the base, and a longitudinally extending slit-shaped groove intervenes between a base part of the movable parts and the side peripheries of the fixing part and the mounting part. Alternatively, the piezoelectric/electrostrictive device can be constructed in such a manner that a laterally and longitudinally extending rectangular opening intervenes between the other end of the fixing part and the one end of the mounting part constituting the base. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape.
In the piezoelectric/electrostrictive device of the third form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part and the mounting part have a flat plate shape; the movable parts are erect by a predetermined height from side peripheries of the fixing part and the mounting part to face each other and extend along the side peripheries of the fixing part and the mounting part; and the movable parts, the fixing part, and the mounting part are positioned within a central space of the connecting part.
The piezoelectric/electrostrictive device can be constructed in such a manner that the central space of the connecting part on a side of the one end of the fixing part is either closed or open. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape. Still further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part and the mounting part constituting the base has a circular arc shape.
The piezoelectric/electrostrictive devices of these forms according to the present invention can employ the following constructions, namely, a construction such that the base is constructed with a flat plate made of metal; a construction such that a central portion, as viewed in a length direction, of the movable parts constituting the base is formed to have a smaller thickness than other portions of the movable parts; a construction such that the movable parts constituting the base has a reinforcing part located at an end thereof on the fixing part side and bent from an upper edge of the end to extend towards and abut against a surface of the fixing part; a construction such that the movable parts constituting the base has a reinforcing part located at an end thereof on the fixing part side and bent from a front edge of the end to extend towards an inner side and abut against a surface of the fixing part; and a construction such that a reinforcing member intervenes between the movable parts on the fixing part constituting the base. Furthermore, the piezoelectric/electrostrictive devices can employ a construction such that the fixing part constituting the base extends from the one end side of the movable parts and is enlarged as compared with a case of being located within the movable parts, and a construction such that the mounting part constituting the base extends from the other end side of the movable parts and is enlarged as compared with a case of being located within the movable parts.
The methods of producing a piezoelectric/electrostrictive device according to the present invention are directed to methods of respectively producing piezoelectric/electrostrictive devices of the above-described three forms, and the methods of producing the piezoelectric/electrostrictive devices of these various forms are as follows.
The first production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the first form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts and the fixing part.
The production method can be carried out in such a manner that the stamped structure has a gate-shaped opening composed of a pair of straight side grooves located at right and left sides of a rectangular flat plate and extending along side peripheries and an opening formed by cutting and removing a portion between the two grooves, and the side peripheries of the flat plate are bent along the side grooves to form the side peripheries into the movable parts and to form a portion between the side grooves into the fixing part.
The second production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the second form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts, the fixing part, and the mounting part.
The production method can be carried out in such a manner that the stamped structure has an H-shaped opening composed of a pair of straight side grooves located at right and left sides of a rectangular flat plate and extending along side peripheries and a straight central groove that connects the two side grooves with each other at a middle part, and the side peripheries of the flat plate are bent along the side grooves to form the side peripheries into the movable parts and to form a portion between the side grooves into the fixing part and the mounting part. Further, the production method can be carried out in such a manner that the stamped structure has a rectangular opening at a central part of a rectangular flat plate, and side peripheries of the flat plate are bent along side peripheries of the opening to form the side peripheries into the movable parts and to form a portion between the side peripheries into the fixing part and the mounting part.
The third production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the third form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts, the fixing part, the mounting part, and the connecting part.
The production method can be carried out in such a manner that the stamped structure has a rectangular flat plate part located inside a central opening of a rectangular flat plate and has an H-shaped opening composed of a pair of straight side grooves located at right and left sides of the flat plate part and extending along side peripheries and a straight central groove that connects the two side grooves with each other at a middle part, and the side peripheries of the flat plate part are bent along the side grooves to form the side peripheries into the movable parts, to form a portion between the side grooves into the fixing part and the mounting part, and to form a portion around the central opening into the connecting part.
The production methods according to the present invention can be carried out in such a manner that a flat plate made of metal is adopted as a material for forming the base, and an opening of the stamped structure is formed by stamping simultaneously with stamping the flat plate or formed by a hole-forming process after stamping the flat plate.
It is essential in the principle of operation that the fixing part or the fixing part and the mounting part are closely connected to the two flexible side peripheries. Since these are integrally formed in the piezoelectric/electrostrictive devices according to the present invention, the most preferable modes are embodied in view of the principle of operation.
For example, in the case where the aforesaid two or three essential parts are made of metal and welded with each other, one must take into consideration the problems in the heat treatment step, such as distortion by heat of welding, deterioration of material quality, and annealing. In contrast, in the case where the base is integrally formed as in the piezoelectric/electrostrictive devices according to the present invention, these fears are absent even if the base is made of metal, and also an improvement in the strength of the connecting part by process hardening at the time of integral forming can be expected.
If the piezoelectric/electrostrictive device according to the present invention is combined with a component (for example, a magnetic head of a hard disk drive), the height after assemblage will not be equal to the sum of the height of the component and the height of the device but will be smaller than the sum, thereby producing an advantage that the device can have a compact construction. Regarding the height of the device, the thickness of the plate of the movable parts and the thickness of the adhesive are added to the height of the component; however, as compared with the known devices described at the beginning, the height after assemblage can be reduced, thereby providing an effect of space reduction. Further, the assemblage can be carried out with ease simply by bonding the component onto the fixing part, and the bonding area can be enlarged, thereby advantageously increasing the bonding strength and providing a structure that will not be easily dropped off by impact.
In the first and second piezoelectric/electrostrictive devices among the piezoelectric/electrostrictive devices according to the present invention, it is easy in view of their structure to form, by pressing, a recess to accommodate an adhesive at the bonding site of the mounting part and the fixing part to the component to be controlled. This can increase the bonding strength and can restrain the squeeze-out of the adhesive. Also, it is easy to form a standard position (hole or the like) for positioning that is used in assembling the component. For this reason, the assembling precision in assembling the component onto the mounting part on the device and in mounting the fixing part onto the gimbal of the suspension in later steps can be increased to further improve the yield of the products. By testing the piezoelectric/electrostrictive element in advance before assembling the device, the deterioration of device characteristics after assembling the device can be greatly reduced.
The piezoelectric/electrostrictive device of the third form according to the present invention can produce the functions and effects that are produced by the first and second piezoelectric/electrostrictive devices. In particular, since the third piezoelectric/electrostrictive device has a connecting part that is integral with the mounting part, the device provides a great advantage that the connecting part can be allowed to function as a gimbal for supporting the magnetic head (slider) of the hard disk drive.
The piezoelectric/electrostrictive devices according to the present invention are based on the piezoelectric/electrostrictive devices of the above-described three forms. In these piezoelectric/electrostrictive devices having a basic structure, the base of each device has an integral structure formed from an original plate made of a flat plate, so that the base is in principle constructed with only one construction component. Therefore, the construction components of each device are two kinds, namely, the base and the piezoelectric/electrostrictive elements, so that the number of construction components of the piezoelectric/electrostrictive device can be greatly reduced, and the number of steps for assembling the construction components can be greatly reduced, thereby leading to large reduction of costs.
Further, in each piezoelectric/electrostrictive device according to the present invention, since the number of construction components is extremely small and the number of bonding sites between the construction components is extremely small, there is little or no variation in the adhesion between the construction components, whereby the piezoelectric/electrostrictive device has device characteristics in which the set precision is high.
Further, in forming each piezoelectric/electrostrictive device according to the present invention, there is no need to adopt means for cutting a device master at numerous sites, so that there is no contamination caused by dusts and other contaminants generated at the time of cutting the device master. For this reason, if the base and the piezoelectric/electrostrictive elements are cleaned in advance in assembling the piezoelectric/electrostrictive device, the assembled piezoelectric/electrostrictive device has little or no contamination, thereby providing a great advantage that the step of cleaning the piezoelectric/electrostrictive device can be omitted or carried out in a simple manner.
Regarding the piezoelectric/electrostrictive devices according to the present invention, the piezoelectric/electrostrictive device of the first form, the piezoelectric/electrostrictive device of the second form, and the piezoelectric/electrostrictive device of the third form can be produced with ease and at a low cost respectively by the first method according to the present invention, the second method according to the present invention, and the third method according to the present invention.